It's me again with a punch suggestion.

http://backpack.tf/classifieds/search/656/11/0

one for 3 keys, one for 3.25 and 5 for 3.5 keys

http://www.tf2outpost.com/trade/9693091 (3.25, has 2, VERY new)

http://www.tf2outpost.com/trade/9689709 (3, 2 hours)

http://www.tf2outpost.com/trade/9620612 (3, 2 days, lowered his price)

http://www.tf2outpost.com/trade/9615046 (3, 2 days)

http://www.tf2outpost.com/trade/9530777 (3, 6 days)

http://www.tf2outpost.com/trade/9554908 (2.75, 5 days, outlier)

unsold at 3.5

http://www.tf2outpost.com/trade/9692843 (fairly new though)

http://www.tf2outpost.com/trade/9687718 (3 hours)

http://www.tf2outpost.com/trade/9379656 (week)

http://www.tf2outpost.com/trade/9669597 (19 hours)

http://www.tf2outpost.com/trade/9677644 (13 hours)

http://www.tf2outpost.com/trade/9654292 (bp.tf price, day)

as we can't see closed trades and I like being a bit conservative I think 3-3.5 is a good range